Alkalinization of amide local anaesthetics by addition of 1% sodium bicarbonate solution

Abstract

for this group of local anaesthetics. This study demonstrates that 1 mL of 1% sodium bicarbonate solution A number of methods exist by which the pH of local may be used to alkalinize this range of local anaesthetic solutions may be increased. Most comanaesthetics without the risk of precipitation. We also monly, these require the addition of differing amounts conclude that Ropivacaine (at concentration 0.75% of sodium bicarbonate solution according to the local and 1.0%), is unsuitable for alkalinization since it preanaesthetic drugs. Sodium bicarbonate (1%) was ticipitates at a pH of 6.0. trated against pH in six commonly used local anaesthetic solutions. Titration curves of pH and vol-Keywords: local anaesthetics, alkalinization, sodium bicarbonate. ume of sodium bicarbonate solution added are shown commercial local anaesthetic solutions is in the

Buffered lidocaine and bupivacaine mixture the ideal local anesthetic solution

“…In the present study, we confirmed that LA solutions containing epinephrine were more acidic than their plain counterparts, consistent with previous reports (3,5,18). In addition to the lower initial pH, various additives, such as sodium metabisulphite and pH adjusters such as hydrochloric acid and sodium hydroxide contribute buffering capacity (16,18).…”

“…Hence, raising the pH closer to pKa increases the fraction of the drug in the nonionized form, increasing the proportion of the administered dose that can enter neurons. This hastens anesthesia onset, reduces pain transmission and, thus, lowers pain perception on LA infiltration into tissues (3,5,8,15,18). Alkalinization also increases intracellular concentration of carbon dioxide, which effectively decreases intracellular pH.…”

“…Alkalinization also increases intracellular concentration of carbon dioxide, which effectively decreases intracellular pH. In more acidic intracellular pH, LAs exist more so in the ionized base form, actively blocking nerve cell sodium channels, thus preventing depolarization and the propagation of action potentials (15,18). The buffering effect on intracellular pH may, thus, also contribute to the more rapid onset of anesthesia reported with alkalinized solutions.…”

“…In addition to the lower initial pH, various additives, such as sodium metabisulphite and pH adjusters such as hydrochloric acid and sodium hydroxide contribute buffering capacity (16,18). Sodium metabisulphite is a strong antioxidant that combines with epinephrine to form an inactive epinephrine sulfonate at pH >4, and is added to prevent the oxidation of epinephrine (7,22).…”

The Effects of Alkalinization of 0.5% Ropivacaine by Adding Sodium Bicarbonate on Block Onset, Ending Time and Quality, and Postoperative Analgesic Efficiency for Peripheral Nerve Block in Unilateral Extremity Surgery

“…In one such study, Milner et al stated that 0.75% and 1% ropivacaine in 1% sodium bicarbonate established precipitation. 15 Since we added 8.4% sodium bicarbonate to the syringe at the precise moment of the procedure, we observed no significant precipitation. Studies regarding alkalinization in lower extremity blocks are very rare.…”